Dental instruments, such as pneumatically driven drills, are normally held by an instrument holder within reach of the dentist. In the past, valve mechanisms have been mounted to the instrument holder for generating and conveying signals to a control system whenever the instrument was removed from and returned to the holder.
FIG. 1 depicts in exemplary prior art instrument holder 20, shown in dashed lines, along with its associated valve mechanism 22, generally shown in solid lines. The instrument holder 20 is shaped to define an opening 24 into which a hand instrument, such as a pneumatically driven drill, can be inserted. The opening 24 is tapered so that as the instrument is lowered within the opening 24, the instrument will contact the walls of the opening and be suspended therefrom until removed by the dentist.
The valve mechanism 22 is mounted inside the instrument holder 20 and is operable for opening and closing a pneumatic valve 26 in response to the respective removal and return of the instrument to the opening 24. This two-state valve 26 is connected via a low-pressure pneumatic line 28 to a control system. Opening or closing of the valve 26 effectively changes the pressure in the line 28, and the control system responds to changes in the pressure by, for example, applying or removing a relatively high air pressure source to the pneumatically driven instrument.
The valve 26 depicted in FIG. 1 includes a generally hollow, cylindrical body 30 to which the pneumatic line 28 is connected to deliver pressurized air to the interior of the body. A valve stem 32 protrudes through an opening 34 in the valve body 30. The base of the stem 32 is enlarged to seal against the opening 34. An internal spring normally forces the valve stem base against the opening 34 with the stem 32 extending along an axis concentric with that opening 34 thereby to close the opening. Whenever the stem 32 is tipped out of the closed position, such as shown in FIG. 1, the base of the valve stem shifts against the opening to let air bleed from the valve body and, hence, from pneumatic line 28. The opening of the valve is thus communicated to the control system by the pressure drop in line 28.
The valve mechanism 22 of the depicted prior device includes a trigger 40 that is pivotally mounted to a pivot tube 42 that is fastened inside the instrument holder 20. A compression spring 44 is mounted between the trigger 40 and the instrument holder for normally urging the tip 46 of the trigger through a slot in the instrument holder so that the tip 46 projects into the opening 24.
The valve body 30 is mounted inside a casing 50 near the trigger 40. A generally tubular extension 52 of the trigger 40 fits over the pivot tube 42 to extend from the trigger to a location next to the protruding stem 32 of the valve 26. The extension 52 includes a projecting boss 54 that is configured and arranged so that when the trigger tip 46 is forced by the spring 44 into the unoccupied opening 24, the boss 54 bears against the stem 32 to tip that stem into the open position as shown in FIG. 1.
Whenever an instrument is placed into the opening 24, the instrument contacts the tip 46 of the trigger, thereby pushing the tip into the instrument holder, compressing the spring 44 and, rotating the boss 54 about tube 42 away from the stem 32 so that the stem resumes the position for closing the valve 26. The closing of the valve is communicated to the control system by the consequent pressure increase in line 28.
The present invention is directed to an instrument holder with valve assembly that is considerably more compact and easier to assemble than the prior art holder and valve mechanisms. The valve assembly is essentially a self-contained unit that is easy to install into the holder. The holder construction is greatly simplified as a result of the self-contained nature of the valve assembly. The valve assembly is adaptable for any of a number of other applications where a two-state, pneumatic control signal may be desired.
The instrument holder into which the valve assembly is mounted is a compact, easily cleaned member. In one embodiment of the instrument holder, multiple openings are formed for holding instruments. At the selection of the user, the openings may or may not carry the associated valve assemblies. A plug is provided for simplifying cleaning of any holder opening that does not have an associated valve assembly.